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Genetic test reveals transplant errors

As many as a quarter of transplanted kidneys are not matched closely
enough to transplant patients because of errors in the matching process.
This mismatching probably accounts for many otherwise unexplained kidney
failures in transplant patients.

These are the conclusions of German immunologist Gerhard Opelz of Heidelberg
University, who coordinated a study of more than 4000 transplants across
Europe and the US. Opelz and his team uncovered the discrepancies with a
recently developed DNA-based tissue-typing technique, which appears certain
to improve matching and extend the life of transplanted kidneys.

Matching relies on identifying the antigens on the surfaces of the cells.
Before a transplant operation, the donor’s and recipient’s antigens are
identified by testing tissue against a bank of some 300 different sera from
people with known antigens. The procedure takes about 5 hours.

Two of the three most important classes of tissue antigen, known as
HLA-A and HLA-B, are easily recognised. The third, HLA-DR, is harder to
identify because it contains many similar variants and is only present in
a few of the body’s cells.

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Opelz compared the standard serological technique with a genetic test
which identifies the genetic variants that code for the different tissue
antigens. He then looked at the outcome of 380 transplants which had previously
been thought to be perfect matches. His genetic technique confirmed that
275 kidneys were matched for all HLA antigens, and around 86 per cent of
these survived at least a year. The remaining 105 were mismatched and only
70 per cent of them survived for a year (The Lancet, 24 August).

Opelz says if typing errors are eliminated, all matched transplants
could be as successful as those between brothers and sisters. Of these,
about 93 per cent survive for more than a year.

On this evidence the number of perfectly matched kidney transplants
in Europe could increase from about 10 per cent to 25 per cent. It also
seems likely that the transplanted kidneys will last longer.

However, the genetic method of matching organs is not likely to become
routine. The test takes several days and with most donors, who are accident
victims, there is not enough time to do the tests before operating.